Gas nozzle for substrate processing chamber

ABSTRACT

A gas delivery nozzle for a substrate fabrication apparatus has a gas delivery tube. The gas delivery tube encloses a gas channel having an asymmetrically tapered aperture. The asymmetrically tapered aperture is defined by (i) a lower lip that projects upwardly into the gas channel to partially block the gas channel and (ii) a upper brim that projects downwardly into the gas channel and overhangs the lower lip.

BACKGROUND

[0001] In the fabrication of electronic circuits, such as integrated circuits and displays, materials such as semiconductor, dielectric and conductor materials are deposited and patterned on a substrate 5. Some of these materials are deposited by chemical vapor deposition (CVD) or physical vapor deposition (PVD) processes, and others may be formed by oxidation or nitridation of substrate materials. For example, in chemical vapor deposition processes, a deposition gas is introduced into a chamber 20 and energized by heat and/or RF energy to deposit a film on the substrate. In physical vapor deposition, a target is sputtered to deposit a layer of the target material on the substrate 5. In etching processes, a patterned mask, comprising a photoresist or hard mask material, is formed on the substrate surface 15 by lithography and subsequent etching, and portions of the substrate surface 15 that are exposed between the mask features are etched by an energized gas, such as a halogen or oxygen containing gas. Such deposition and etching processes, and additional planarization processes, are conducted in a sequence to process the substrate 5 to fabricate integrated circuits and other electronic devices.

[0002] In one type of conventional process chamber, a gas delivery tube 10 is used to introduce process gas from a gas supply into the chamber 20, as illustrated in FIG. 1 (Prior Art). The gas delivery tube 10 typically comprises a gas outlet 25 in the chamber 20 that injects the process gas 40 (which may be a single gas or a premixed mixture of gases) into a process zone of the chamber 20. The gas delivery tube 10, passes through the sidewall 30 of the chamber 20 and injects gas laterally into the chamber 20 from a gas outlet 25 located at a periphery of the substrate 5. However, as shown in the figure, a portion of the injected gas 40 travels to a ceiling 35 of the chamber 20 and forms undesirable deposits 18 on the ceiling surface. These deposits 18 have to be cleaned by shutting down the chamber 20 and manually scraping off the deposits or using plasma cleaning gas processes, both of which increase chamber down time, which is undesirable in circuit fabrication.

[0003] The laterally injected process gas may also fail to reach the central portion of the substrate 5 in the same concentration levels as that reaching the edge of the substrate 5. The gas delivery tube 10 ejects the process gas 40 in an angular density distribution that often does not cover the substrate surface 15 with sufficient uniformity. This can result in little or no deposition at the center of the substrate surface 15. Thus, a second gas delivery tube 45 is sometimes provided above the center of the substrate 5 to direct process gas 40 towards the central substrate portion. However, the additional gas delivery tube 45 increases the costs of the chamber 20 because the ceiling 35 to pass the gas delivery tube 45 therethrough, especially when the ceiling 35 that has to be drilled through is made of a ceramic material. Also, the gas delivery tubes 10, 45 can block the line of sight of interferometric endpoint detection systems (not shown) located above the chamber ceiling 35. Additionally, the overhead gas delivery tube 45 may interfere with the transmission of RF energy that may be applied from an induction antenna 50 above the ceiling 35.

[0004] Thus, it is desirable to have a gas delivery tube that minimizes deposition on the ceiling surface of the chamber 20, provides good uniformity of deposition across the substrate surface 15, and does not excessively increase the cost of fabricating the chamber 20.

SUMMARY

[0005] A gas delivery nozzle for a substrate fabrication apparatus comprises a gas delivery tube. The gas delivery tube encloses a gas channel having an asymmetrically tapered aperture. The asymmetrically tapered aperture is defined by (i) a lower lip that projects upwardly into the gas channel to partially block the gas channel and (ii) a upper brim that projects downwardly into the gas channel and overhangs the lower lip.

[0006] A substrate fabrication apparatus comprises a chamber having a substrate support to support a substrate in the chamber. A gas distributor introduces a process gas into the chamber. The gas distributor comprises a gas delivery nozzle in the chamber, the gas delivery nozzle comprising a gas delivery tube that encloses a gas channel having an asymmetrically tapered aperture. The asymmetrically tapered aperture is defined by (i) a lower lip that projects upwardly into the gas channel to partially block the gas channel and (ii) a upper brim that projects downwardly into the gas channel and overhangs the lower lip. A gas energizer energizes the process gas to process the substrate. A gas exhaust exhausts the process gas from the chamber.

DRAWINGS

[0007]FIG. 1 (Prior Art) is a partial sectional side view of conventional gas delivery tubes in a process chamber, showing an undesirable gas flow pattern provided by the gas delivery tubes; and

[0008]FIG. 2 is a partial sectional side view of a gas delivery tube according to the present invention in an embodiment of a process chamber of a substrate fabrication apparatus, showing the desirable gas flow pattern provided by the gas delivery tube.

DESCRIPTION

[0009] A substrate processing chamber 140 of a substrate fabrication apparatus 200 comprises an improved gas delivery nozzle 110 to uniformly and efficiently distribute process gas 102 across a substrate 145 while minimizing formation of excessive residue deposits on the ceiling 150 of the chamber 140, as illustrated in FIG. 2. The exemplary embodiment of the substrate fabrication apparatus 200 illustrated in the figure, comprises a substrate support 142 to support the substrate in the chamber 140. A gas distributor 226 comprises a process gas supply 210 that is provided to supply the process gas 102 for the processing of the substrate 145 into the chamber 140. A flow valve 220 adjusts the flow of process gas from the gas supply 210 into the chamber 140. A gas energizer 228 comprises an antenna 230 or electrode that applies a fluctuating electromagnetic field to the process gas 102 to energize the process gas and thereby process the substrate 145. An energizer power supply 240 supplies an alternating current to the antenna 230 or electrode to generate the fluctuating electromagnetic field, and a controller 250 is provided to regulate the flow of the process gas into chamber 140 and to control energizing of the process gas 102. A gas exhaust (not seen) exhausts the process gas from the chamber 140.

[0010] The gas delivery nozzle 110 may be positioned to the side of the substrate 145 to aim the process gas flow across and over the surface 155 of the substrate 145. The gas delivery nozzle 110 extends from the sidewall 180 to direct the process gas laterally toward the substrate 145.

[0011] The gas delivery nozzle 110 comprises a gas delivery tube 165 that encloses a gas channel 120 through which the process gas 102 is passed. The gas channel 120 terminates in an asymmetrically tapered aperture 130, as shown in the figure. The gas delivery tube 165 has a central axis 125, and an asymmetrically tapered aperture 130 is provided at the end of the tube 165 to define an opening that is offset from, and radially asymmetric about, the central axis 125 of the gas delivery tube 165. The asymmetrically tapered aperture 130 ejects the process gas asymmetrically away from the ceiling 150 of the chamber 140, and toward the substrate surface 155, in a spray pattern that reduces deposition of material on the ceiling or etching of the ceiling 150 and also improves uniformity of gas distribution over the substrate surface 155.

[0012] The asymmetrically tapered aperture 130 comprises a lower lip 170 that projects upwardly into the gas channel 120 to partially block the gas channel 120. For example, the lower lip 170 may comprise a protuberance that extends from the tube wall and into the gas channel. The protuberance can have a crescent shape that defines the bottom edge of the tapered aperture 130. The lower lip 170 upwardly guides lower laminae 121 of the gas stream, increasing the velocity, and decreasing the pressure, of these lower laminae 121 to guide the gas stream away from the chamber ceiling 150, as shown in the figure. The upper and lower laminae 122, 121 of the gas flow in the gas channel 120 are forced through the main portion of the channel at substantially uniform pressure and velocity. As the lower laminae 121 approach the asymmetrically tapered aperture 130, they are obstructed and guided upwardly by the lower lip 170. The lower lip 170 may be a uniformly sloped protuberance, as shown in the figure, or alternatively the protuberance may be curved to more gradually alter the velocity of the obstructed process gas 102.

[0013] The asymmetrically tapered aperture 130 further comprises an upper brim 175 that projects downwardly into the gas channel 120 and overhangs the lower lip 170. For example, in one embodiment the upper brim extends beyond the lower lip by at least about 1 mm. As the upper and lower laminae 122, 121 approach the ejection point, the lower laminae 121 impinge on the upper laminae 122 from below with high velocity, causing the process gas to be redirected into the projecting upper brim 175 overhanging the lower lip 170 at high velocity. The projecting upper brim 175 causes the process gas to be reflected downwardly, away from the chamber ceiling 150 and towards the substrate surface 155, thus reducing problematic deposition onto, or etching of, the chamber ceiling 150. The upper brim can also comprise a protuberance that extends downwardly from the tube wall into the volume of the gas channel 120. The protuberance can comprise a gentle hump with a raised portion in the middle and depressions in the side. This causes the upper laminae 122 to be directed downwardly toward the periphery of the substrate. As a result of the combination of the upper laminae, which more efficiently cover the substrate periphery, and the lower laminae, which more efficiently cover the central portion of the substrate, the gas delivery nozzle 110 generates a more uniform distribution of process gas across the substrate surface.

[0014] The asymmetric design of the tapered outlet 130 also allows the tapered outlet 130 to direct the process gas substantially towards the substrate surface 165 with a desirable angular density distribution to cover the substrate surface 165 substantially uniformly. As the process gas exits the asymmetrically tapered aperture 130, the lower lip 170 asymmetrically obstructs the flow of the process gas, inwardly redirecting the lower laminae in the outer region of the gas flow to increase the gas density in the center of the gas flow stream, as shown in FIG. 2. The asymmetrically tapered aperture 130 also imparts an asymmetry to the density distribution of the gas flow stream, which compensates for the asymmetrical positioning of the gas delivery nozzle 110 to one side of the substrate 145. The asymmetrically tapered aperture 130 concentrates the gas that is projected toward the central region 185 above the center of the substrate surface 155, resulting in improved exposure of the central portion of the substrate surface 155, and thus substantially uniform coverage of the substrate 145. In one embodiment, the asymmetrically tapered aperture 130 is shaped to deliver the majority of the process gas below the central axis 125 of the gas delivery tube 165. In contrast, the conventional gas nozzles, as illustrated in FIG. 1 (Prior Art), cause the process gas to bloom outwardly and substantially symmetrically upon ejection, resulting in a centrally deficient portion of the stream that insufficiently exposes the central portion of the substrate surface 155. The improved gas delivery nozzle 110 ejects the process gas from the nozzle 115 toward the substrate 145 in a spray pattern that is radially asymmetric about the central axis 125 of the gas delivery nozzle 110, preventing the process gas from detrimentally and wastefully streaming towards the ceiling 150 of the process chamber 140, and also improving the uniformity of coverage of the substrate surface 155.

[0015] The lower lip 170 of the asymmetrically tapered aperture 130 can also have a slanted external face 135, as shown in FIG. 2. After the process gas 102 is ejected from the asymmetrically tapered aperture 130 and is then decelerated, a region of high pressure forms in the process gas adjacent to the external slanted face 135 of the lower lip 170. The pressurized gas in this region applies a force to the lower lip 170, and the lower lip 170 applies an equal and opposite force to the gas in the high pressure region in a direction normal to, and away from, the lower lip 170, directing the process gas at a downward angle toward the substrate 145. The external slanted face 135 of the lower lip 170 serves as a springboard for the process gas after the process gas is projected from the opening 190 of the asymmetrically tapered aperture 130. For example, the external slanted face 135 of the asymmetrically tapered aperture 130 may be at an angle of less than 90° in relation to the central axis 125 to achieve a desirable angular distribution of mass flow. The external slanted face 135 may even be at an angle of at least about 5° in relation to the central axis 125 to achieve a more desirable angular distribution.

[0016] The gas delivery nozzle 110 is adapted to eject the process gas from the asymmetrically tapered aperture 130 toward the substrate 145 in a desirable spray pattern that prevents the process gas from detrimentally and wastefully streaming towards the ceiling 150 of the chamber 140, and improves the uniformity of coverage of the substrate surface 155. This gas nozzle design also significantly reduces the formation of process deposits on the ceiling 150 of the chamber 140. As a result, the chamber 140 could be cleaned less often and operated for longer hours between cleaning cycles. 

We claim:
 1. A gas delivery nozzle for a substrate fabrication apparatus, the gas delivery nozzle comprising: a gas delivery tube enclosing a gas channel having an asymmetrically tapered aperture defined by: (i) a lower lip that projects upwardly into the gas channel to partially block the gas channel, and (ii) a upper brim that projects downwardly into the gas channel and overhangs the lower lip.
 2. The gas delivery nozzle of claim 1 wherein the lower lip comprises an external slanted face that is at an angle of at least about 5° in relation to a central axis of the gas delivery tube along the gas channel.
 3. The gas delivery nozzle of claim 2 wherein the external slanted face is at an angle of less than 90°.
 4. The gas delivery nozzle of claim 1 wherein the upper brim extends beyond the lower lip by at least about 1 mm.
 5. The gas delivery nozzle of claim 1 wherein the asymmetrically tapered aperture comprises a center that is offset below the central axis of the gas delivery tube.
 6. The gas delivery nozzle of claim 1 wherein the lower lip comprises a protuberance having a crescent shape.
 7. A substrate fabrication apparatus comprising: a chamber having a substrate support to support a substrate in the chamber; a gas distributor to introduce a process gas into the chamber, the gas distributor comprising a gas delivery nozzle in the chamber, the gas delivery nozzle comprising a gas delivery tube that encloses a gas channel having an asymmetrically tapered aperture, the asymmetrically tapered aperture defined by: (i) a lower lip that projects upwardly into the gas channel to partially block the gas channel, and (ii) a upper brim that projects downwardly into the gas channel and overhangs the lower lip; a gas energizer to energize the process gas to process the substrate; and a gas exhaust to exhaust the process gas from the chamber.
 8. The apparatus of claim 7 wherein the lower lip comprises an external slanted face that is at an angle of at least about 5° in relation to a central axis of the gas delivery tube along the gas channel.
 9. The apparatus of claim 8 wherein the external slanted face is at an angle of less than 90°.
 10. The apparatus of claim 7 wherein the upper brim extends beyond the lower lip by at least about 1 mm.
 11. The apparatus of claim 7 wherein the asymmetrically tapered aperture comprises a center that is offset below the central axis of the gas delivery tube.
 12. The apparatus of claim 7 wherein the lower lip comprises a protuberance having a crescent shape. 